Wireless devices, such as user equipment (UEs), detect system information (SI) of neighboring cells in Evolved Universal Mobile Telecommunications System (UMTS) Terrestrial Radio Access (E-UTRA). The SI includes a Master Information Block (MIB) and System Information Block Type 1 (SIB1) that the UE uses to identify the Cell Global Identifier (CGI) of a new cell. The MIB is transmitted on the Physical Broadcast Channel (PBCH). The MIB is transmitted in subframe 0 with a periodicity of 40 ms and 4 redundancy versions are transmitted within this period. The SIB1 is multiplexed into the Physical Downlink Shared channel (PDSCH). The SIB1 is transmitted on subframe 5 and it has a periodicity of 80 ms. If the UE has previously detected the new cell, the UE may already know the Physical Cell Identity (PCI) of the new cell.
The method of detecting the CGI may be the same for frequency division duplex (FDD), half duplex FDD (HD-FDD), and time division duplex (TDD). A UE may read SI for the acquisition of CGI during measurement gaps that are autonomously created by the UE.
In Long Term Evolution (LTE), the MIB is transmitted on the broadcast channel (BCH) and includes a limited number of the most essential and most frequently transmitted parameters that are needed to acquire other information from the cell. For example, the MIB may include downlink (DL) bandwidth, physical hybrid automatic repeat request (HARQ) indication channel (PHICH) configuration, and system frame number (SFN).
The MIB is transmitted periodically with a periodicity of 40 ms and repetitions are transmitted within the 40 ms period. The first transmission of the MIB is scheduled in subframe 0 of radio frames for which the SFN modulo 4=0, and repetitions are scheduled in subframe 0 of all other radio frames.
In LTE, the SIB1 may include, for example, public land mobile network (PLMN) identity, cell identity, closed subscriber group (CSG) identity and indication, frequency band indicator, SI-window length, and scheduling info for other SIBs.
The LTE SIB1 may indicate whether a change has occurred in the SI messages. The UE is notified about a coming change in the SI by a paging message, from which the UE will know that the system information will change at the next modification period boundary. The modification period boundaries are defined by SFN values for which SFN modulo m=0, where m is the number of radio frames comprising the modification period. The modification period is configured by system information.
The LTE SIB1, as well as other SIB messages, is transmitted on the downlink shared channel (DL-SCH). The SIB1 is transmitted with a periodicity of 80 ms and repetitions are transmitted within the 80 ms period. The first transmission of SIB1 is scheduled in subframe 5 of radio frames for which the SFN modulo 8=0, and repetitions are scheduled in subframe 5 of all other radio frames for which SFN modulo 2=0.
In case of inter-radio access technology (inter-RAT) UMTS Terrestrial Radio Access Network (UTRAN), the UE reads the MIB and System Information Block Type 3 (SIB3) of the target UTRAN cell to acquire its CGI.
To support mobility, a UE identifies a number of neighbor cells and reports their physical cell identity (PCI) to a serving network node (e.g., serving eNodeB in E-UTRAN). The serving network node may request the UE to report neighbor cell measurements such as Reference Signal Received Power (RSRP) and/or Reference Signal Received Quality (RSRQ) in E-UTRAN or common pilot channel (CPICH) Received signal Code Power (RSCP) and/or CPICH Ec/No in UTRAN or GSM EDGE Radio Access Network (GERAN) carrier received signal strength indication (RSSI) or pilot strength for code division multiple access 2000 (CDMA2000)/high rate packet data (HRPD). In response to the reported UE measurement, the serving network node sends handover command to the UE.
With small cell sizes in dense deployment scenarios (e.g., femto cells, restricted small cells like femto closed subscriber group, pico cells, etc.), PCIs are frequently reused. To prevent a handover (HO) command to a non-allowed home base station (e.g., CSG cell), the serving network node may also request the UE to decode and report the CGI of the target cell. This may be referred to as home inbound mobility. The CGI is unique in the network facilitating the network to distinguish between macro base station (BS) and home BS or to uniquely identify that the reported cell belongs to a CSG.
The procedure and the associated requirements for the target cell's CGI reporting are specified in E-UTRAN. One aspect of CGI decoding is that it is performed by the UE during the autonomous gaps, which are created by the UE itself. A reason for acquiring the target cell CGI during autonomous gaps is because a typical UE is not able to simultaneously receive the data from the serving cell and acquire the target cell's system information, which contains the CGI. Furthermore, CGI acquisition of an inter-frequency or inter-RAT target cell requires the UE to switch the carrier frequency. Thus, autonomous gaps are used for acquiring the target cell's CGI. The autonomous gaps are created both in uplink and downlink.
FIG. 1 illustrates autonomous gaps for acquisition of system information. The particular example illustrates E-UTRA FDD MIB and SIB1 acquisition. The 3GPP TS 36.133 standard assumes that a UE performs automatic gain control (AGC) on a target carrier before reading MIB and also before SIB1, and that 5 subframes may be blanked for performing AGC. Moreover, the standard assumes that 3 blocks from MIB and 3 redundancy versions from SIB1, from the same 40 and 80 ms period, respectively, are needed. Because the starting position of each acquisition is unknown, 5 gaps each with duration of 4 subframes are allocated for each MIB and SIB1 acquisition.
Using the self-organizing network (SON) function in E-UTRAN, network operators can automatically plan and tune network parameters and network nodes. A previous method was based on manual tuning, which is time and resource intensive requiring considerable work force involvement. Because of network complexity, large number of system parameters, multiple inter-radio access technologies (IRATs), etc., a method to test the self-organization in the network is advantageous.
A network operator may also add or delete a cell or a base station (with multiple cells). For example, during an early phase of network deployment new cells may be added more frequently than in later stages. In later stages, an operator may upgrade the network by adding more carriers or more base stations on the same carrier. The operator may also add cells related to another technology. When network elements are added or deleted, neighbor relation tables may change. An automatic approach for updating neighbor relation tables may be referred to as automatic neighbor cell relation (ANR) establishment and is part of the SON function. To ensure correct establishment of the neighbor cell relation, the serving cell requests the UE to report the CGI of the new target cell. The UE identifies the PCI of the new target cell and reports it back to the serving cell. During CGI acquisition, the UE reads the target cell's system information during autonomous gaps. Similar to home inbound mobility, CGI acquisition for ANR also interrupts the data from the serving cell.
E-UTRAN specifies Evolved CGI (ECGI) for intra-frequency ECGI reporting and inter-frequency ECGI reporting. In addition, E-UTRAN is expected to specify ECGI for inter-RAT UTRAN CGI reporting.
A UE is required to report an intra-frequency ECGI within about 150 ms from receiving a target intra-frequency cell SINR of at least −6 dB or higher. During the acquisition of the target cell's ECGI on the serving carrier frequency, the UE is allowed to create autonomous gaps in the downlink and uplink. Under continuous allocation the UE is required to transmit certain number of ACK/NACK on the uplink to ensure that the UE does not create excessive gaps.
The UE is also required to report an inter-frequency ECGI within about 150 ms from receiving a target inter-frequency cell SINR of at least −4 dB or higher. During the acquisition of the target cell's ECGI on the serving carrier frequency, the UE is allowed to create autonomous gaps in the downlink and uplink. This causes the UE to interrupt downlink reception and uplink transmission in the serving cell. Under continuous allocation, the UE is also required to transmit certain number of ACK/NACK on the uplink to ensure that the UE does not create excessive gaps.
In UTRAN, the target cell's CGI acquisition is much longer. For example, the target cell's CGI acquisition may be more than 1 second depending upon the periodicity of the SIB3, which contains the CGI. Furthermore, due to the autonomous gaps created by the UE to acquire the target cell's CGI, the interruption of the data transmission and reception from the serving cell can be 600 ms or longer.
Machine-to-machine (M2M) communication (also referred to as machine type communication (MTC)) establishes communication between machines and/or between machines and humans. The communications may comprise exchange of data, signaling, measurement data, configuration information, etc. The device size may vary from that of a wallet to that of a base station. The M2M devices are quite often used for applications like sensing environmental conditions (e.g., temperature reading, etc.), metering or measurement (e.g., electricity usage, etc.), fault finding or error detection, etc. In these applications the M2M devices are active for a short duration depending upon the type of service, such as about 200 ms every 2 seconds, about 500 ms every 60 minutes, or any other suitable period. The M2M device may also measure other frequencies or other RATs.
In general, MTC devices tend to be of low cost and low complexity. A low complexity UE that may be used for M2M operation may implement one or more low cost features, such as smaller downlink and uplink maximum transport block size (e.g., 1000 bits) and/or reduced downlink channel bandwidth of 1.4 MHz for data channel (e.g., PDSCH). A low cost UE may also comprise of a half-duplex (HD-FDD) and one or more of the following additional features: single receiver (1 Rx) at the UE, smaller downlink and/or uplink maximum transport block size (e.g., 1000 bits), and reduced downlink channel bandwidth of 1.4 MHz for data channel. The low cost UE may also be referred to as a low complexity UE.
Path loss between an M2M device and a base station can be large in some scenarios. For example, path loss may be large for an M2M device in a remote location (such as an M2M sensor or metering device located in the basement of a building). In such scenarios receiving a signal from the base station may be challenging. For example, the path loss can be 20 dB worse than normal operation. Enhanced coverage in uplink and downlink may alleviate such challenges. Examples of techniques in the UE and/or in the radio network node for enhancing the coverage include transmit power boosting, repetition of transmitted signal, applying additional redundancy to the transmitted signal, use of advanced/enhanced receiver, etc. In general, when employing coverage enhancing techniques, the M2M may be referred to as operating in “coverage enhancing mode.” A low complexity UE (e.g., UE with one receiver) may also be capable of supporting enhanced coverage mode of operation.